Heart rate-index estimates aerobic metabolism in professional soccer players

This study aimed at proposing a new heart rate (HR) method to track aerobic metabolism in soccer by: (i) validating a recently developed HR index (HR_index) in professional soccer players, (ii) comparing HR_index vs the most common HR parameters and (iii) testing the agreement between measured and estimated VO₂ values using HR_index.

cross-sectional.

184 professional soccer players performed a step incremental running test on a treadmill while VO₂ and HR were recorded. HR_index was calculated (actual HR/resting HR) and its relationship with VO₂ was compared with the relationships with the metabolism of actual HR, net HR, and % of HR reserve. Finally, HR_index was used to predict VO₂=((HR_index·6)-5)·3.5) and measured and estimated VO₂ were compared by 2W RM-ANOVA and Bland-Altman analysis.

HR_index/VO₂ relationship explained 85% of the variability in data, showing a higher performance than actual HR (77%) and similar values to the other parameters. Measured and estimated VO₂ were not significantly different ≤14kmh^-1, whereas at speeds ≥14kmh^-1 measured VO₂ was higher than estimated VO₂. Finally, measured and estimated VO₂ were highly correlated (R²=0.85, p=0.000), and showed no significant bias (bias=-1.03, z=-0.69, precision=3.75mlkgmin^-1).

We validated the HR_index/VO₂ relationship in professional soccer players. HR_index showed better agreement with metabolism than actual HR and similar agreement to the other HR parameters. HR_index allowed to estimate VO₂, but at very high-intensity HR_index underestimated VO₂. Future studies should test this in real game conditions. HR_index could offer a time-efficient and easy-to-use "field" method to monitor aerobic metabolism in soccer.